Gasket-forming plastisols comprising vinyl chloride resin, epoxy plasticizer, diester plasticizer and filler



United States Patent 3,356,625 GASKET-FORMIN G PLASTISOLS COMPRISINGVINYL CHLORIDE RESIN, EPOXY PLASTI- CIZER, DIESTER PLASTICIZER ANDFILLER Donald A. Giessler, Center Township, Ind, assignor to BailBrothers Company, Inc., Muncie, Ind, 21 corporation of Indiana NoDrawing. Continuation of application Ser. No. 277,690, May 3, 1963,which is a continuation of application Ser. No. 197,848, May 28, 1962.This application July 11, 1966, Ser. No. 564,432

7 Claims. (Cl. 260-23) ABSTRACT OF THE DISCLOSURE A polyvinyl chlorideplastisol gasket-forming composition having unusually high filler ratioswith workable viscosities as a result of the use of a criticalplasticizer composition including an epoxidized unsaturated natural oiland a dialkyl diester of sebacate acid, adipic acid, and azelaic acid,and a closure employing such a gasket-forming plastisol composition.

This application is a continuation of application Ser. No. 277,690,filed May 3, 1963, which application is in turn a continuation ofapplication Ser. No. 197,848, filed May 28, 1962, both said applicationsnow being abandoned.

This invention relates to a gasket composition and, more particularly,to a vinyl plastisol composition which is particularly useful in forminga gasket in a closure for a glass jar or the like.

Vinyl plastisols have found relatively wide usage in providing gasketsfor closures for glass jars and the like. They can be introduced into anenameled closure, in the region where a seal between the finish of a jaror the like and the closure is desired, heated for a very short periodof time, cg. three minutes or less, and then cooled to provide acompleted gasket. Certain problems have been encountered, however, withrespect to compositions which are safe for use in packaging foods. Onlya relatively few plasticizers are acceptable in plastisols which maycome into contact with food, and such plasticizers have only limitedvariations in properties and effect. Certon plasticizers which areacceptable for all other reasons are less acceptable due to the tasteand/or odor characteristics they introduce. As a consequence, it hasheretofore been necessary to control the plastisol composition withinrelatively narrow limits in order to achieve a commercially workablecomposition. For example, only a relatively small proportion of a fillercan be incorporated in the compositions and still retain a workableviscosity.

The instant invention is based upon the discovery of a particularplastisol composition wherein a significantly higher proportion offiller can be employed than was heretofore possible. The invention isalso based upon the discovery that the viscosity of the plastisolcomposition, and, therefore, the amount of filler that can be employedtherewith, can be varied by changes in the relative proportions of theconstituents of the composition.

It is, therefore, an object of the invention to provide a new andimproved plastisol composition.

It is a further object of the invention to provide a novel plastisolcomposition that is particularly useful in producing gaskets in closuresfor glass jars and the like.

It is another object of the invention to provide an improved plastisolcomposition which is of such a nature that seal impressions are readilymade by the glass finish in contact with the gasket with or without theaid of heating the cap prior to application on the jar.

Other objects and advantages will be apparent from the description whichfollows, which is intended only to 3,356,625 Patented Dec. 5, 1967illustrate and disclose, and in no way to limit, the invention.

The gasket composition of the invention generally comprises a plastisolmixture comprising a vinyl polymer composition, a filler and acombination of plasticizers. The plasticizer combination,advantageously, includes an epoxide plasticizer and a diesterplasticizer.

The epoxide plasticizers may be epoxidized unsaturated organic compoundssuch as olefins, and particularly olefins having isolated double bondsor double bonds near alkyl groups, e.g., fats, oils, esters, etc.Advantageously, the epoxide plasticizers are epoxidized oils such assoybean oil, linseed oil, safllower oil, and the like. Preferably, theepoxides have an iodine number not greater than 6 and an oxirane oxygenof at least 6 percent.

The diester plasticizers employed in combination with the epoxide may bediesters of dibasic acids such as sebacic acid, adipic acid, azelaicacid, and the like, with the sebacates being preferred, Particularlyuseful as diester plasticizers in the gasket composition of theinvention are diesters of sebacic acid with C to C alkyl alcohols,diesters of azelaic acid with C to C alkyl alcohols, and diesters ofadipic acid with C to C alkyl alcohols and mixtures thereof.

The vinyl polymer composition of the plastisol gasket compositionaccording to the invention advantageously is formed by emulsion orsuspension polymerization techniques, and then spray dried. The emulsionpolymerization produces dense spherical particles having a diameter ofthe order of about 1-2 microns, while the suspension polymerizationproduces larger, e.g. about 10 microns, particles which are otherwisesimilar. The particles are easily dispersible in plasticizers, but notdissolved thereby until the temperature is raised to about 300-400" F.In commercial practice they are most often polyvinyl chlorides orcopolymers of vinyl chloride, for example with vinyl acetate orvinylidene chloride, although other dispersible vinyl polymers,copolymers or mixtures can also be used. Copolymers are more likely tobe produced by suspension polymerization, and homopolymers by emulsionpolymerization.

As has been indicated above, the composition according to the inventionincludes a filler such as calcium carbonate or barium sulfate. Bariumsulfate is the preferred filler because it i substantially completelyinert under conditions to which a gasket for a glass jar or the likecontaining food is ordinarily subjected in use. Calcium carbonate, onthe other hand, is reactive with acidic foods, evolving carbon dioxidewhich can develop a superatmospheric pressure under certain conditions.However, calcium carbonate is entirely satisfactory for use in a gasketcomposition which does not come into contact with acidic foods inservice. Other fillers can also be used but at 'a sacrifice to optimumplastisol viscosity at normal room temperature.

Operable, preferred and optimum ranges of proportions of ingredients inthe plastisol gasket composition ac cording ot the invention are withinthe approximate ranges set forth in Table I, below:

TABLE I Parts Operable Preferred Optimum Vinyl polymer compositionPlasticizer composition Filler equivalent on a volume basis to theindicated number of parts of barium sulfate 100 100 -300 -240 About; 215

275-325 About 300 3 Operable, preferred and optimum proportions of thediester plasticizer and the epoxide plasticizer in the compositionaccording to the invention are within the approximate ranges set forthin Table 11, below:

TABLE II Parts Operable Preferred Optimum Diester 25-100 40450 50Epoxide 100 200 150-180 165 The following procedure was used to producea plastisol gasket composition from a dispersible vinyl chloride resin,a dispersible vinyl chloride-vinylidene chlo- Satisfactory plastisolshave also been produced by the same method and from substantially thesame ingredients, except that different epoxidized soybean oilplasticizers were used. These plasticizers varied in iodine number from0.6 to 0.9, and in oxi-rane oxygen from 6.3 percent to 7.0 percent.

Similar results have also been achieved using 428 parts of the bariumsulfate filler instead of the 300 parts, and using 428 partsof thebarium sulfate filler and 115 parts and 190 parts of the epoxidizedsoybean oil plasticizer with 100 parts and .25 parts, respectively, ofdibutyl sebacate. Similarly, 100 parts of the vinyl chloride resin havebeen used in the foregoing procedure in place of the mixture of vinylchloride and copolymer resins.

The dispersion according to the invention producedas described inExample 1, above, was used to form a gasket in a closure for a glass jarby injecting about a 1600 milligram portion thereof into a groove nearthe periphery of the closure, and heating the closure and the dispersionto a temperature of approximately 350 F. for about two minutes.

Example 2 The procedure described in Example 1, above, has also beenemployed to produce other plastisol dispersion gasket compositionsaccording to the invention. Representative formulations that have beenused are set forth in Table III, below:

TABLE III Diisobutyl adipate Di-n-hexyl azolato Expoxidized soybean oilExpoxidized linseed oil, B ariurn sulfate Calcium carbonate PlastisolNo.

l The vinyl chloride-vinyl chloride vinylidene chloride blend of 60 andparts, respectively, of the vinyl chloride resin and of mer of Example01 No. 7 has also been made with different vinyl resin, e.g., byblending, of the vinyl chloride resin of Example 1 and of a commerciallyavailable medium molecte resin with 40 parts of a vinyl chloride-vinylacetate copolymer, by blending of Example 1, and by blending 40 parts 60parts of the paste resin and with the 2 The vinyl resin was achloride-vinylidene chloride copoly N .b.: The formulation of Plastisrespectively, 60 parts ular weight polyvinyl chloride pas the pasteresin with the oopolyme able vinyl copolymer resins with ride copolymerresin, dibutyl sebacate, an epoxidized soybean oil, barium sufate, andother ingredients for pigmentation, lubrication, and stabilization.

A high speed mixer was used to produce a plastisol from 58 parts of thepolyvinyl chloride resin, 42 parts of the vinyl chloride-vinylidenechloride copolymer resin, 165 parts. of the epoxidized soybean oil,parts of dibutyl sebacate and 300 parts of the barium sulfate, pluspigments, lubricants aud stabilizers. Mixing was continued until auniform dispersion had been produced. This dispersion had a viscosity of3000 centipoises at room temperature, and was suited for use inproducing gaskets in closures by commercial techniques at roomtemperature and at elevated temperatures.

1 The dispersible vinyl chloride resin had an average particle size ofabout 1 to 2 microns, 100 percent thereof being finer than 200 mesh,U.S. Sieve series, and was of relatively high molecular weight, a 60percent solution thereof in a blended alcohol phthala'te (an average of8 carbon atoms in the alcohol) plasticizer having a viscosity of about4000 centipoises. The specific viscosity of the resin was about 0.6.

The dispersible vinyl cllloride-vinylidene chloride copolymer resin hadan average particle size of about 10 microns, and was of a medium to lowmolecular weight, having a specific gravity of about 0.4.

The cpoxidized soybean oil had an iodine number of 0.7 and an oxiraneoxygen of 6.8 percent.

The barium sulfate was a fine powder, substantially all of the particlesof which were smaller than 12 microns; it lngulgg specific gravity of4.40 and an oil absorption rating 0 copolymer blend of Example 1 wasused. 1 the vinyl of various other commercially availvinyl chlorideresin of Example 1.

As has been indicated above, whenever dibutyl sebacate is replaced byanother sebacate plasticizer or by an adipate or azelate plasticizer,there is some sacrifice in quality of the plastisol gasket composition.This sacrifice may involve one or more of the following: (1) an increasein viscosity of the composition, which increases the difficulty ofgasket formation, (2) the imparting of a slight odor to the composition,when in the form of a gasket, or (3) the imparting of a slight taste tofoods which come into contact with the final gasket. These phenomena.are sufficiently slight that the other plasticizers can be used withacceptable results which are unexpected and unobvious at the high fillerlevels used in compositions according to the instant invention, and bycomparison with previously known plastisol compositions. However, suchcompositions containing dibutyl sebacate, in the indicated proportions,are unexpectedly useful and unobvious even by comparison with thosecontaining the other sebacates and the adipates and azelatescontemplated hereby. Examples of other sebacate, adipate and azelateplasticizers which can be used in the foregoing formulations includedibutyl adipate,. di-n-hexyl adipate, dicapryl adipate,di-(Z-ethylhexyl) adipate, dinonyl adipate, octyl decyl adipates,di-decyl adipates, di(rnethylcyclohexyl) adipate, di-Z-cthylbutylazelate, di-Z-ethylhexyl azelate, di-isooctyl azelate, di-isobutylazelate, dioctyl sebacate, di-isooctyl sebacate, di-Z-ethylhexyliso-sebacate and mixed alcohol sebacates where the mixed alcohols havean average of from 4 to 8 carbon atoms. Mixtures of the plasticizers canalso be employed.

It will be apparent that various changes and modifications can be madefrom the specific details set forth herein Without departing from thespirit and scope of the invention as set forth in the appended claims.

What I claim is:

1. A gasket-forming composition adapted for use with a metal closure,said composition comprising a plastisol mixture of:

(A) about 215 parts of a plasticizer composition,

(a) said plasticizer composition consisting essentially of about 50parts of dibutyl sebacate and about 165 parts of an epoxidized soybeanoil having an iodine number not greater than 6, and an oxirane oxygencontent of at least 6 percent,

(B) 100 parts of a vinyl chloride polymer dispersed in the plasticizercomposition, and

(C) about 300 parts of a barium sulfate filler.

2. A gasket-forming composition adapted for use with a metal closure,said composition comprising a plastisol mixture of:

(A) from 190 to 240 parts of a plasticizer composition,

(a) said plasticizer composition consisting essentially of from 40 to 60parts of a dialkyl sebacate and from 150 to 180 parts of an epoxidizedunsaturated natural oil having an iodine number not greater than 6, andan oxirane oxygen content of at least 6 percent,

(B) 100 parts of a vinyl chloride polymer dispersed in the plasticizercomposition, and

(C) from 275 to 325 parts of a barium sulfate filler.

3. A gasket-forming composition adapted for use with a metal closure,said composition comprising a plastisol mixture of:

(A) from 190 to 240 parts of a plasticizer composition,

(a) said plasticizer composition consisting essentially of from 40 to 60parts of a dialkyl sebacate and from 150 to 180 parts of an epoxidizedunsaturated natural oil,

(B) 100 parts of a vinyl chloride polymer dispersed in the plasticizercomposition, and

(C) an amount of a filler selected from the group consisting of calciumcarbonate and barium sulfate which is equivalent on a volume basis tofrom 275 to 325 parts of barium sulfate.

4. A gasket-forming composition adapted for use with a metal closure,said composition comprising a plastisol mixture of:

(A) from 125 to 300 parts of a plasticizer composition,

(a) said plasticizer composition consisting essentially of from 25 to100 parts of at least one plasticizer selected from the group consistingof diesters of sebacic acid with C to C alkyl alcohols diesters ofazelaic acid with C to C alkyl alcohols, and diesters of adipic acidwith C to C alkyl alcohols and from 100 to 200 parts of an epoxidizedunsaturated natural oil having an iodine number not greater than 6, andan oxirane oxygen content of at least 6 percent, (B) 100 parts of avinyl chloride polymer dispersed in the plasticizer composition, and (C)an amount of a filler selected from the group consisting of calciumcarbonate and barium sulfate Which is equivalent on a volume basis tofrom 150 to 450 parts of barium sulfate. 5. A gasket-forming compositionadapted for use with a metal closure, said composition comprising aplastisol mixture of:

(A) from 125 to 300 parts of a plasticizer composition,

(a) said plasticizer composition consisting essentially of from 25 to100 parts of an alkyl diester of an acid selected from the groupconsisting of sebacic acid, adipic acid and azelaic acid, and from 100to 200 parts of an epoxidized unsaturated natural oil. (B) 100 parts ofa vinyl chloride polymer dispersed in the plasticizer composition, and(C) an amount of filler selected from the group consisting of calciumcarbonate and barium sulfate which is equivalent on a volume basis tofrom 150 to 450 parts of barium sulfate. 6. A gasket-forming compositionadapted for use with a metal closure, said composition comprising aplastisol mixture of:

(A) from 125 to 300 parts of a plasticizer composition,

(a) said plasticizer composition consisting essentially of from 25 to100 parts of an alkyl diester of an alkyl dibasic acid and from 100 to200 parts of an epoxidized unsaturated natural oil, (B) 100 parts of avinyl chloride polymer dispersed in the plasticizer composition, and (C)an amount of a filler selected from the group consisting of calciumcarbonate and barium sulfate which is equivalent on a volume basis tofrom 150 to 450 parts of barium sulfate. 7. A metal closure having asealing gasket produced by hardening the plastisol mixture claimed inclaim 6.

References Cited UNITED STATES PATENTS 2,654,913 10/1953 Maier 26023 X2,880,901 4/ 1959 Zipper 215-4O 2,967,162 1/1961 Vasta 26021 2,980,6434/1961 Edelman et al 26023 X 2,993,920 7/1961 Budde et al 260233,002,641 10/ 1961 Normandy 215-40 3,005,433 10/1961 Risch 215-403,061,130 10/1962 Husum 26023 X 3,202,307 8/1965 Rainer et al. 260-233,231,529 1/ 1966 Kuhn et a1. 26023 X 3,283,936 11/1966 Kehe et a1.21540 DONALD E. CZAJA, Primary Examiner. LEON J. B-ERCOVITZ, Examiner.R. A. WHITE, Assistant Examiner.

6. A GASKET-FORMING COMPOSITION ADAPTED FOR USE WITH A METAL CLOSURE,SAID COMPOSITION COMPRISING A PLASTISOL MIXTURE OF: (A) FROM 125 TO 300PARTS OF A PLASTICIZER COMPOSITION, (A) SAID PLASTICIZER COMPOSITIONCONSISTING ESSENTIALLY OF FROM 25 TO 100 PARTS OF AN ALKYL DIESTER OF ANALKYL DIBASIC ACID AND FROM 100 TO 200 PARTS OF AN EPOXIDIZEDUNSATURATED NATURAL OIL, (B) 100 PARTS OF A VINYL CHLORIDE POLYMERDISPERSED IN THE PLASTICIZER COMPOSITION, AND (C) AN AMOUNT OF A FILLERSELECTED FROM THE GROUP CONSISTING OF CALCIUM CARBONATE AND BARIUMSULFATE WHICH IS EQUIVALENT ON A VOLUME BASIS TO FROM 150 TO 450 PARTSOF BARIUM SULFATE.